Source and Chemistry of Hydroxymethanesulfonate (HMS) in Fairbanks, Alaska

Abstract

is a subarctic city with fine particle (PM 2.5 ) concentrations that exceed air quality regulations in winter due to weak dispersion caused by strong atmospheric inversions, local emissions, and the unique chemistry occurring under the cold and dark conditions. Here, we report on observations from the winters of 2020 and 2021, motivated by our pilot study that showed exceptionally high concentrations of fine particle hydroxymethanesulfonate (HMS) or related sulfur-(IV) species (e.g., sulfite and bisulfite). We deployed online particle-into-liquid sampler−ion chromatography (PILS-IC) in conjunction with a suite of instruments to determine HMS precursors (HCHO, SO 2 ) and aerosol composition in general, with the goal to characterize the sources and sinks of HMS in wintertime Fairbanks. PM 2.5 HMS comprised a significant fraction of PM 2.5 sulfur (26−41%) and overall PM 2.5 mass concentration of 2.8−6.8% during pollution episodes, substantially higher than what has been observed in other regions, likely due to the exceptionally low temperatures. HMS peaked in January, with lower concentrations in December and February, resulting from changes in precursors and meteorological conditions. Strong correlations with inorganic sulfate and organic mass during pollution events suggest that HMS is linked to processes responsible for poor air quality episodes. These findings demonstrate unique aspects of air pollution formation in cold and humid atmospheres.

Wintertime spatial patterns of particulate matter in Fairbanks, AK during ALPACA 2022

“…Other PM types, including secondary particulate pollution ( e.g. hydroxymethanesulfonate, HMS 12 ) have been shown to be important as well, though the spatial patterns of PM components or their gas-phase precursors are unknown.…”

Stability assessment of organic sulfur and organosulfate compounds in filter samples for quantification by Fourier Transform-Infrared Spectroscopy

“…During severe winter haze in the North China Plain, HMS was measured using real-time single particle mass spectrum instruments and filter-based IC methods during periods of high SO2 and HCHO concentrations and low oxidant concentrations in particles with high liquid water content (Ma et al, 2020). Very high concentrations of HMS have been measured in Fairbanks, Alaska during pollution events in a cold, dark and humid environment (Campbell et al, 2022). In the Interagency Monitoring of Protected Visual Environments (IMPROVE) Network, there is evidence of an ubiquitous presence of HMS in ion chromatograms of samples collected at 150 sites in the United States (Moch et al, 2020).…”

“…High-resolution aerosol mass spectrometry (HR-AMS) has been used to measure HMS and organosulfates, however the majority of compounds mostly fragment into inorganic sulfate and a non-sulfur containing organic fraction, leading to an underestimation of HMS and overestimation of inorganic sulfate (Dovrou et al, 2019;Song et al, 2019). HMS has been measured in field and laboratory studies by IC (Campbell et al, 2022;Dovrou et al, 2019), however notable challenges have been documented. HMS and sulfate are not fully resolved in all IC methods (Campbell et al, 2022) leading to poor resolution that can introduce error into the results for both HMS and sulfate (Dovrou et al, 2019;Ma et al, 2020).…”

“…HMS has been measured in field and laboratory studies by IC (Campbell et al, 2022;Dovrou et al, 2019), however notable challenges have been documented. HMS and sulfate are not fully resolved in all IC methods (Campbell et al, 2022) leading to poor resolution that can introduce error into the results for both HMS and sulfate (Dovrou et al, 2019;Ma et al, 2020). In IC methods where HMS and sulfate are well resolved, HMS and sulfite may be unresolved and co-elute with bisulfite (Moch et al, 2018;Wei et al, 2020).…”

“…cloud, fog, pH), can contribute to HMS sample mass loss off the filter leading to an underestimation of HMS (Moch et al, 2020). With proper columns and eluent composition, IC has been shown to separate HMS and sulfate peaks with only a small underestimation of HMS due to sulfate conversion (Campbell et al, 2022;Dovrou et al, 2019). At least one laboratory study (published in Japanese) has characterized HMS by FT-IR (Sato et al, 1984) but FT-IR has not been used to measure HMS in ambient aerosol samples to the best of our knowledge.…”